Adenoviral gene transfer of interleukin 12 into tumors synergizes with adoptive T cell therapy both at the induction and effector level

Intratumor Adoptive Transfer of IL-12 mRNA Transiently Engineered Antitumor CD8+ T Cells

Retroviral gene transfer of interleukin-12 (IL-12) into T cells markedly enhances antitumor efficacy upon adoptive transfer but has clinically shown unacceptable severe side effects. To overcome the toxicity, we engineered tumor-specific CD8⁺ T cells to transiently express IL-12. Engineered T cells injected intratumorally, but not intravenously, led to complete rejections not only of the injected lesion but also of distant concomitant tumors. Efficacy was further enhanced by co-injection with agonist anti-CD137 mAb or by transient co-expression of CD137 ligand. This treatment induced epitope spreading of the endogenous CD8⁺ T cell immune response in a manner dependent on cDC1 dendritic cells. Mouse and human tumor-infiltrating T lymphocyte cultures can be transiently IL-12 engineered to attain marked immunotherapeutic effects.

Revisiting Interleukin-12 as a Cancer Immunotherapy Agent

IL12 antitumor activities are mediated by the activation of T and natural killer (NK) lymphocytes to produce IFNγ. Systemically, recombinant IL12 has a narrow therapeutic window that favors local delivery, for instance, by gene therapy approaches. IL12 is a powerful partner in immunotherapy combinations with checkpoint inhibitors and adoptive T-cell transfer. Clin Cancer Res; 24(12); 2716-8. ©2018 AACRSee related article by Hu et al., p. 2920.

Neoadjuvant administration of Semliki Forest virus expressing interleukin-12 combined with attenuated Salmonella eradicates breast cancer metastasis and achieves long-term survival in immunocompetent mice

BACKGROUND

Metastatic breast cancer is a major cause of death among women worldwide; therefore efficient therapeutic strategies are extremely needed. In this work we have developed a gene therapy- and bacteria-based combined neoadjuvant approach and evaluated its antitumor effect in a clinically relevant animal model of metastatic breast cancer.

METHODS

2×10(8) particles of a Semliki Forest virus vector expressing interleukin-12 (SFV-IL-12) and/or 2×10(7) units of an aroC (-) Samonella Typhimurium strain (LVR01) were injected into 4T1 tumor nodules orthotopically implanted in mice. Tumors were surgically resected and long-term survival was determined. IL-12 and interferon-γ were quantified by Enzyme-Linked ImmunoSorbent Assay, bacteria was visualized by inmunohistochemistry and the number of lung metastasis was calculated with a clonogenic assay.

RESULTS

SFV-IL-12 and LVR01 timely inoculated and followed by surgical resection of tumors succeeded in complete inhibition of lethal lung metastasis and long-term survival in 90% of treated mice. The combined therapy was markedly synergistic compared to each treatment alone, since SFV-IL-12 monotherapy showed a potent antiangiogenic effect, being able to inhibit tumor growth and extend survival, but could not prevent establishment of distant metastasis and death of tumor-excised animals. On the other hand, LVR01 alone also showed a significant, although limited, antitumor potential, despite its ability to invade breast cancer cells and induce granulocyte recruitment. The efficacy of the combined therapy depended on the order in which both factors were administered; inasmuch the therapeutic effect was only observed when SFV-IL-12 was administered previous to LVR01, whereas administration of LVR01 before SFV-IL-12 had negligible antitumor activity. Moreover, pre-treatment with LVR01 seemed to suppress SFV-IL-12 antiangiogenic effects associated to lower IL-12 expression in this group. Re-challenged mice were unable to reject a second 4T1 tumor; however 100% of them could be totally cured by applying the same neoadjuvant combined regimen. To our knowledge, these are the most encouraging results obtained to date in a post-operatory setting using the highly aggressive 4T1 animal model.

CONCLUSIONS

SFV-IL-12-based gene therapy combined with Salmonella LVR01 neoadjuvant administration has a synergic antitumor effect and may be a promising therapeutic option to prevent and/or eradicate pre-operatory metastasis in locally advanced breast cancer.

Transient depletion of specific immune cell populations to improve adenovirus-mediated transgene expression in the liver

BACKGROUND & AIMS

Adenoviral (Ad) vectors are currently one of the most efficient tools for in vivo gene transfer to the liver. However, anti-Ad immune responses limit the safety and efficacy of these vectors. The initial inflammatory reaction is a concern in terms of toxicity, and it favours the development of cellular and humoral responses leading to short transgene persistence and inefficient vector re-administrations. Therefore, safe and simple ways to interfere with these processes are needed. Study ways to deplete specific immune cell populations and their impact on liver-directed gene transfer.

METHODS

First-generation Ad vectors encoding reporter genes (luciferase or β-galactosidase) were injected intravenously into Balb/c mice. Kupffer cells and splenic macrophages were depleted by intravenous administration of clodronate liposomes. B lymphocytes, CD4(+) , CD8(+) T lymphocytes or NK cells were depleted by intraperitoneal injection of anti-M plus anti-D, anti-CD4, anti-CD8 or anti-asialo-GM1 antibodies respectively. Long-term evolution of luciferase expression in the liver was monitored by bioluminescence imaging.

RESULTS

The anti-CD4 monoclonal antibody impaired cellular and humoral immune responses, leading to efficient vector re-administration. Clodronate liposomes had no impact on humoral responses but caused a 100-1000 fold increase in liver transduction, stabilized transgene expression, reduced the concentration of inflammatory cytokines, and inhibited lymphocyte activation.

CONCLUSIONS

Transient CD4(+) T-cell depletion using antibodies is a clinically feasible procedure that allows efficient Ad redosing. Systemic administration of clodronate liposomes may further increase the safety and efficacy of vectors.

Immunotherapy for liver tumors: present status and future prospects

Increasing evidence suggests that immune responses are involved in the control of cancer and that the immune system can be manipulated in different ways to recognize and attack tumors. Progress in immune-based strategies has opened new therapeutic avenues using a number of techniques destined to eliminate malignant cells. In the present review, we overview current knowledge on the importance, successes and difficulties of immunotherapy in liver tumors, including preclinical data available in animal models and information from clinical trials carried out during the lasts years. This review shows that new options for the treatment of advanced liver tumors are urgently needed and that there is a ground for future advances in the field.

Locoregional treatment of malignant hepatic tumors with biologic response modifiers

Locoregional delivery of biologic response modifiers (BRMs) to hepatic tumors is an appealing approach to increase the dwell time of BMRs, to minimize the systemic toxicity, and to induce local and possibly systemic immune responses against tumor cells. Previous clinical studies using this approach showed some encouraging results. However, a large-scale clinical trial is needed to prove the efficacy of locoregional BMR treatment in primary and metastatic hepatic tumors. Combination of various BRM agents with appropriate treatment modalities might further improve the efficacy of locoregional BMR treatment. Additionally, we need to collect more information regarding the host immune response and change in tumor microenvironment after delivering BMRs to hepatic tumors.

Human adenovirus replicates in immunocompetent models of pancreatic cancer in Syrian hamsters

The preclinical evaluation of toxicity and antitumor effect of conditionally replicative (oncolytic) adenoviruses is hampered by the inability of human adenoviruses to replicate efficiently in murine cells. The Syrian golden hamster (Mesocricetus auratus) has been suggested as a permissive animal for adenoviral replication, and cancer cell lines derived from various hamster tumors are available. We provide evidence that wild-type adenovirus type 5 is able to infect and replicate in the pancreatic cancer cell lines HaP-T1 and H2T both in vitro and in vivo. Determination of cytopathic effect, viral spread, progeny production, and the expression of late viral proteins indicates that the complete viral cycle of adenovirus takes place, albeit less efficiently than in highly permissive human cancer cell lines A549 and HuH7. Intrahepatic inoculation of HaP-T1 and H2T cells gave rise to tumors in the liver of hamsters that resemble metastases of pancreatic cancer. The growth of HaP-T1-induced nodules was faster compared with those derived from H2T, but both caused progressive liver infiltration and peritoneal dissemination. When adenovirus was inoculated in these lesions, productive replication took place and newly formed infective virions could be recovered 4 days after administration. In conclusion, the Syrian hamster models described here offer the opportunity to evaluate the effect of oncolytic adenoviruses in an immunocompetent animal and may be a valuable tool in the preclinical evaluation of these agents.

Eradication of hepatoma and colon cancer in mice with Flt3L gene therapy in combination with 5-FU

We developed a recombinant defective adenovirus with an insert of gene encoding extracellular domain of mouse Flt3L (Ad-mFlt3L) under control of cytomegalovirus promoter to investigate the biological efficacy of Flt3L in combination with chemotherapeutical drug, 5-FU, in eliciting an effective anti-cancer immunity in mouse hepatoma and colon cancer model systems. The constructed Ad-mFlt3L efficiently infected hepatoma and colon cancer cells both in vitro and in vivo, leading to a high production of mFlt3L proteins in association with accumulation of DCs, NK cells and lymphocytes in local tumor tissues. Administration of Ad-mFlt3L can protect bone marrow injury caused by 5-Fu and stimulates proliferation and maturation of lymphocytes, APCs and NKs. Intratumoral injection of Ad-mFlt3L followed by an intraperitoneal administration of 5-Fu significantly inhibited tumor growth and cured established tumors. Adenovirus mediated Flt3L gene therapy synergies with chemotherapeutic drug, 5-Fu, in elicitation of long-lasting antitumor immunity. The tumor specific immunity can be adoptively transferred into naïve animals successfully by transfusion of CD3+CD8+ T cells from the treated mice. The data suggests that adenovirus mediated Flt3L gene therapy in combination with 5-Fu chemotherapy may open a new avenue for development of anti-cancer chemogenetherapy.

Cloning and characterization of an adenoviral vector for highly efficient and doxycycline-suppressible expression of bioactive human single-chain interleukin 12 in colon cancer

BACKGROUND

Interleukin-12 (IL-12) is well characterized to induce cellular antitumoral immunity by activation of NK-cells and T-lymphocytes. However, systemic administration of recombinant human IL-12 resulted in severe toxicity without perceptible therapeutic benefit. Even though intratumoral expression of IL-12 leads to tumor regression and long-term survival in a variety of animal models, clinical trials have not yet shown a significant therapeutic benefit. One major obstacle in the treatment with IL-12 is to overcome the relatively low expression of the therapeutic gene without compromising the safety of such an approach. Our objective was to generate an adenoviral vector system enabling the regulated expression of very high levels of bioactive, human IL-12.

RESULTS

High gene expression was obtained utilizing the VP16 herpes simplex transactivator. Strong regulation of gene expression was realized by fusion of the VP16 to a tetracycline repressor with binding of the fusion protein to a flanking tetracycline operator and further enhanced by auto-regulated expression of its fusion gene within a bicistronic promoter construct. Infection of human colon cancer cells (HT29) at a multiplicity of infection (m.o.i.) of 10 resulted in the production of up to 8000 ng/106 cells in 48 h, thus exceeding any published vector system so far. Doxycycline concentrations as low as 30 ng/ml resulted in up to 5000-fold suppression, enabling significant reduction of gene expression in a possible clinical setting. Bioactivity of the human single-chain IL-12 was similar to purified human heterodimeric IL-12. Frozen sections of human colon cancer showed high expression of the coxsackie adenovirus receptor with significant production of human single chain IL-12 in colon cancer biopsies after infection with 3*107 p.f.u. Ad.3r-scIL12. Doxycycline mediated suppression of gene expression was up to 9000-fold in the infected colon cancer tissue.

CONCLUSION

VP16 transactivator-mediated and doxycycline-regulated expression of the human interleukin-12 gene enables highly efficient and tightly controlled cytokine expression in human cancer. These data illustrate the potential of the described adenoviral vector system for the safe and superior expression of therapeutic genes in the treatment of colorectal cancer and other malignancies.

Cell adhesion and cancer: is there a potential for therapeutic intervention?

Carcinogenesis involves a disruption in adhesion molecule expression and tissue architecture, and tumour invasion requires adhesion-dependent migration into surrounding tissues. Therefore, a variety of peptide and antibody-based reagents that block integrins, cadherins, immunoglobulin superfamily and selectin adhesion molecules have been developed to treat cancers. Therapeutics directed at adhesion molecules can block interactions between tumour cells, endothelial cells and immune cells to prevent tumour cell invasiveness and metastasis. Blocking the adhesion molecules that facilitate the invasion of tumours by endothelial cells and immune cells can prevent tumour-associated angiogenesis and the recruitment of immune-mediated growth factors which are required for tumour growth and spread. In addition, targeted therapies using anticancer agents attached to antibodies or peptides directed as tumour-specific adhesion molecules are being developed.

The mechanism of exogenous B7.1-enhanced IL-12-mediated complete regression of tumors by a single electroporation delivery

Electroporation-based mono-gene therapy has received great interest in recent years but coadministration of different therapeutic genes for treatment of tumors has not been well explored. We hypothesize that electroporation is capable of delivering multiple genes that induce an additive or synergistic antitumor effect. To test this hypothesis, we used mice that were bearing SCCVII or TRAMP tumors. Established tumors with a diameter of 4-5 mm were injected with control plasmid DNA or plasmid DNA encoding B7.1, IL-12 or both via electroporation. Tumor regression, CTL activity and the level of B7.1, IL-12 and Stat1 expression were determined in both wild-type mice and in mice with a knock-out of the Stat1 gene. Remarkably, a single coadministration of the plasmids that encoded IL-12 and B7.1 eradicated tumors in 80% of mice. The therapeutic effect was associated with high levels of endogenous B7.1 expression, activity of cytotoxic lymphocytes, and activation of Stat1. Both exogenous B7.1 and IL-12 were required for inducing a high level of Stat1 activation in tumors, which occurred through a mechanism that was independent of the host Stat1. Both stimulators were also required for inducing the strong cytotoxic lymphocyte activity and for increasing the level and extending the duration of endogenous B7.1 expression. We therefore propose a 2-signal stimulation model to explain the synergistic effect of the coadministration of IL-12 and B7.1 on the regression of the tumors.

Gene therapy of liver cancer

The application of gene transfer technologies to the treatment of cancer has led to the development of new experimental approaches like gene directed enzyme/pro-drug therapy (GDEPT), inhibition of oncogenes and restoration of tumor-suppressor genes. In addition, gene therapy has a big impact on other fields like cancer immunotherapy, anti-angiogenic therapy and virotherapy. These strategies are being evaluated for the treatment of primary and metastatic liver cancer and some of them have reached clinical phases. We present a review on the basis and the actual status of gene therapy approaches applied to liver cancer.

New therapies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC), one of the most common cancers worldwide, is often diagnosed at an advanced stage when most potentially curative therapies such as resection, transplantation or percutaneous and transarterial interventions are of limited efficacy. The fact that HCC is resistant to conventional chemotherapy, and is rarely amenable to radiotherapy, leaves this disease with no effective therapeutic options and a very poor prognosis. Therefore, the development of more effective therapeutic tools and strategies is much needed. HCCs are phenotypically and genetically heterogeneous tumors that commonly emerge on a background of chronic liver disease. However, in spite of this heterogeneity recent insights into the biology of HCC suggest that certain signaling pathways and molecular alterations are likely to play essential roles in HCC development by promoting cell growth and survival. The identification of such mechanisms may open new avenues for the prevention and treatment of HCC through the development of targeted therapies. In this review we will describe the new potential therapeutic targets and clinical developments that have emerged from progress in the knowledge of HCC biology, In addition, recent advances in gene therapy and combined cell and gene therapy, together with new radiotherapy techniques and immunotherapy in patients with HCC will be discussed.

Therapeutic effects of adoptive splenocyte transfer following in situ AdIL-12 gene therapy in a mouse prostate cancer model

We developed a preclinical prostate cancer model to study the feasibility of adoptive immunotherapy for residual tumor following neo-adjuvant in situ adenoviral-vector-mediated interleukin 12 (AdIL-12) gene therapy. Splenocytes were obtained from mice with orthotopic 178-2 BMA metastatic mouse prostate cancers treated previously with AdIL-12, or a vector with the IL-12 genes plus the costimulatory gene B7-1 (AdIL-12/B7), or a control gene (Adbetagal). The splenocytes were subsequently injected intravenously into syngeneic mice bearing orthotopic 178-2 BMA tumors generated 3 days previously. Significant orthotopic tumor growth suppression was achieved with splenocytes derived from mice whose tumors had been injected with AdIL-12 compared to splenocytes from control Adbetagal mice (P = 0.0005) and splenocytes from AdIL-12/B7-treated mice significantly suppressed spontaneous lung metastases compared to splenocytes from control mice (P = 0.0356). Adoptive transfer of splenocytes from either AdIL-12 (P = 0.004) or AdIL-12/B7 (P = 0.009)-treated mice significantly prolonged survival relative to controls. Transfer of NK and tumor-specific CTL activities was detected and depletion of CD4+ and CD8+ T cells by in vitro antibody-mediated complement lysis of the splenocytes prior to injection abrogated the effects. Systemic IL-12 administration delivered by intramuscular AdIL-12 injection enhanced the antitumor effects of adoptive splenocyte transfer and boosted the CTL response. Our data provide evidence that this form of adoptive immunotherapy can enhance the effectiveness of neo-adjuvant in situ IL-12 gene therapy in cases of persistent malignancy.

Treatment of hepatocellular carcinoma with adenoviral vector-mediated Flt3 ligand gene therapy

Fms-like tyrosine kinase 3 ligand (Flt3L) plays an important role in development and activation of dendritic cells (DCs) and natural killer cells (NK). It has been shown that administration of either tumor cells transfected in vitro with Flt3L vectors or soluble Flt3L fusion protein in a high dose can enhance host antitumor immunity in animal model systems. In this study, we developed a recombinant defective adenovirus with an insert of gene encoding extracellular domain of mouse Flt3L (Ad-mFlt3L) under control of cytomegalovirus promoter and investigated its biological efficacy in eliciting tumor-specific immune response against hepatocellular carcinoma in mouse hepatoma model. The constructed Ad-mFlt3L efficiently infected hepa 1-6 hepatoma cells both in vitro and in vivo, leading to a high production of mFlt3L proteins in association with accumulation of DCsNK cells and lymphocytes in local tumor tissues. Tumor cells infected with Ad-mFlt3L lost tumorigenicity and became more immunogenic in syngeniec animal models. Intratumoral injection of Ad-mFlt3L (10(9) expression-forming unit) x 3 significantly inhibited tumor growth with elicitation of long-lasting antitumor immunity, which is both preventive and curative. The tumor-specific immunity can be partially abrogated by depletion of either CD3+CD4+ T cells or NK cells and can be also re-established in naïve animals by adoptive transfer of splenocytes from treated mice. The results suggest that adenovirus-mediated Flt3L gene therapy may provide a useful strategy for treatment of cancers.

An oncolytic adenovirus controlled by a modified telomerase promoter is attenuated in telomerase-negative cells, but shows reduced activity in cancer cells

The promoter for human telomerase reverse transcriptase (hTERTp) is preferentially active in malignant cells. It was recently used to control the expression of the adenoviral E1A gene for the development of oncolytic adenoviruses. To ensure maximal repression in normal cells, the inclusion of additional E-boxes in the proximal region of the core promoter was described. We found that the transcriptional activity of this artificial sequence (T-255-4DEB) is minimal in normal cells, but it is also reduced in all the cancer cell lines tested. The cancer specificity of a new oncolytic adenovirus based in this promoter (AdTE1) was evaluated by direct comparison with wild-type adenovirus type 5 (AdWT) in vitro and in vivo. In all the parameters tested, AdTE1 was attenuated in normal cells, but the efficacy in cancer cells showed a parallel reduction, suggesting a lack of specificity. However, the cytotoxicity of AdTE1 was repressed in senescent cells compared to AdWT. Therefore, we conclude that AdTE1 is preferentially attenuated only in cells that are permanently devoid of telomerase expression such as senescent cells. Further modifications in the telomerase-based promoters should be introduced in order to combine maximal attenuation of oncolytic adenoviruses in normal tissues and enhanced activity in tumors.

Future therapies for hepatocellular carcinoma

A large proportion of patients with advanced hepatocellular carcinoma (HCC) lack effective therapy. Due to chemoresistance, hope has focused on other approaches including targeted therapies, immune stimulants, and the emerging area of gene therapy. Increasing efforts in basic and clinical development of these approaches will hopefully result in more efficient therapies against HCC.

Effects of recombinant adenovirus-mediated expression of IL-2 and IL-12 in human B lymphoma cells on co-cultured PBMC

Background

Modulation of the immune system by genetically modified lymphoma cell vaccines is of potential therapeutic value in the treatment of B cell lymphoma. However, the anti-tumor effect of any single immunogene transfer has so far been limited. Combination treatment of recombinant IL-2 and IL-12 has been reported to be synergistic for inducing anti-tumor responses in solid tumors but the potential of IL-2/IL-12 gene modified B cell lymphoma cells has not been explored yet.

Methods

Using three different human B cell lymphoma cell lines and primary samples from patients with B cell neoplasms, expression levels of the coxsackie B-adenovirus receptor (CAR) and alpha (v) integrins were analyzed by fluorescence-activated cell sorter (FACS). Adenoviral transduction efficiencies were determined by GFP expression analysis and IL-2 and IL-12 cytokine production was quantified by enzyme-linked immunosorbent (ELISA) assays. Proliferative activities of peripheral blood mononuclear cells (PBMC) stimulated with either cytokine derived from supernatants of transduced lymphoma cells were measured by cell proliferation (MTT) assays. An EuTDA cytotoxicity assay was used to compare cytotoxic activities of IL-2 and/or IL-12 stimulated PBMC against unmodified lymphoma cells.

Results

We found that B cell lymphoma cell lines could be transduced with much higher efficiency than primary tumor samples, which appeared to correlate with the expression of CAR. Adenoviral-expressed IL-2 and IL-12 similarly led to dose-dependent increases in proliferation rates of PBMC obtained from healthy donors. IL-2 and/or IL-12 transduced lymphoma cells were co-cultured with PBMC, which were assayed for their cytolytic activity against unmodified lymphoma cells. We found that IL-2 stimulated PBMC elicited a significant anti-tumor effect but not the combined effect of IL-2/IL-12 or IL-12 alone.

Conclusion

This study demonstrates that the generation of recombinant adenovirus modified lymphoma cell vaccines based on lymphoma cell lines expressing IL-2 and IL-12 cytokine genes is technically feasible, induces increases in proliferation rates and cytotoxic activity of co-cultured PBMC, and warrants further development for the treatment of lymphoma patients in the future.

Biologic therapy of liver tumors

Nonresectable primary and metastatic liver tumors are common malignancies that lack therapies allowing substantial prolongation of survival. Recent progress in molecular and cell biology has opened the way to novel therapies based on biological modifiers, gene transfer, and autologous stem cells. It is now possible to transfer therapeutic genes to the tumor or pericancerous tissue, and to control their expression for long periods of time. It is also feasible to generate autologous endothelial progenitor cells that can be recruited by tumoral vessels acting as vehicles to convey therapeutic genes to the interior of the tumor mass. Combination of biological modifiers, gene therapy, and cell therapy will hopefully provide efficient means to combat inoperable neoplasms in a not-very-distant future.

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Improving efficacy of interleukin-12-transfected dendritic cells injected into murine colon cancer with anti-CD137 monoclonal antibodies and alloantigens

Intralesional administration of cultured dendritic cells (DCs) engineered to produce IL-12 by in vitro infection with recombinant adenovirus frequently displays eradicating efficacy against established subcutaneous tumors derived from the CT26 murine colon carcinoma cell line. The elicited response is mainly mediated by cytolytic T lymphocytes. In order to search for strategies that would enhance the efficacy of the therapeutic procedure against less immunogenic tumors, we moved onto malignancies derived from the inoculation of MC38 colon cancer cells that are less prone to undergo complete regression upon a single intratumoral injection of IL-12-secreting DCs. In this model, we found that repeated injections of such DCs, as opposed to a single injection, achieved better efficacy against both the injected and a distantly implanted tumor; that the use of semiallogeneic DCs that are mismatched in one MHC haplotype with the tumor host showed slightly better efficacy; and that the combination of this treatment with systemic injections of immunostimulatory anti-CD137 (4-1BB) monoclonal antibody achieved potent combined effects that correlated with the antitumor immune response measured in IFN-gamma ELISPOT assays. The elicited systemic immune response eradicates concomitant untreated lesions in most cases. Curative efficacy was also found against some tumors established for 2 weeks when these strategies were used in combination. These are preclinical pieces of evidence to be considered in order to enhance the therapeutic benefit of a strategy that is currently being tested in clinical trials. Supplementary Material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html.

Tumor necrosis factor-related apoptosis-inducing ligand gene on human colorectal cancer cell line HT29

AIM: To evaluate the therapeutic efficiency of Tumor Necrosis Factor-related Apoptosis-inducing Ligand (TRAIL) gene on human colorectal cancer cell line HT29.

METHODS: Human embryonal kidney cells transformed by introducing sheared fragments of Ad5 DNA (293 cell) were used for amplification of adenoviral vectors: Ad/GT-TRAIL, Ad/GT-Bax, Ad/GT-LacZ and Ad/PGK-GV16. Human colorectal cancer cell line HT29 was transfected with binary adenovirus-mediated TRAIL gene. Bax gene was used as positive control, LacZ gene was used as the vector control, and cells treated with PBS only were used as a mock control. The morphological changes, cell growth and apoptosis were measured by reversmicroscope, MTT method and flow cytometry.

RESULTS: All adenoviral vectors titer determined by optical absorbency at A260nm were 1 × 10¹⁰ viral particle/ml(vp/ml). Obviously morphological changes of HT29 cells were observed when infected with Ad/GT-TRAIL, and these changes were much more obviously when Ad/PGK-GV16 was coinfected. The cell suppression percentage and the percentage of apoptotic cells were 52.5% and 16.5% respectively when infected with Ad/GT-TRAIL alone, while combining with Ad/PGK-GV16, the growth of HT29 was suppressed by 85.2% and the percentage of apoptotic cells was 35.9%. It showed a significantly enhanced therapeutic efficiency with binary system (P < 0.05).

CONCLUSION: A binary adenoviral vector system provides an effective approach to amplify viral vectors that express potentially toxic gene, TRAIL. Ad/GT-TRAIL showed a significantly enhanced therapeutic efficiency for HT29 when coinfected with Ad/PGK-GV16. Ad/GT-TRAIL could induce apoptosis of HT29 and inhibit its growth.

Gene therapy of neoplastic liver diseases

Since advanced liver cancer lacks effective therapy in most cases, a considerable interest has been drawn towards gene therapy. Natural or chimerical genes can be transferred to the tumour itself, the non-tumoral liver, or even distant tissues using a variety of vectors administered by intratumoral or intravascular routes. The desired selectivity in gene expression can be achieved by increasing the specificity of gene delivery or by controlling gene expression with tumour-specific promoters, such as alpha-fetoprotein or carcinoembryonic antigen. There are two main approaches to gene therapy of liver cancer aiming at killing directly malignant cells or at improving the host's defensive systems, respectively. The former include replacing the lost function of tumour suppressor genes, inhibiting the action of activated oncogenes, sensitising tumour cells to prodrugs, or infecting the tumoral tissue with viruses that replicate selectively in cancer cells. Host defences can be improved by stimulating the antitumoral immune response, or by interfering with tumour vessel formation. Progress in gene therapy of liver cancer depends very much on information collected from well-designed clinical trials. This information includes knowledge of whether an efficient gene transfer has been achieved and what is the duration and magnitude of gene expression in the transduced tissues. Hopefully, magnetic resonance or positron emission tomography (PET) may turn out to be reliable procedures for tracing transgene expression in humans. Pre-clinical evidence and early clinical trials strongly suggest that there is a place for gene therapy of liver malignancies.

Clinical implications of antigen transfer mechanisms from malignant to dendritic cells. exploiting cross-priming

Expansion and activation of cytolytic T lymphocytes bearing high-affinity T-cell receptors specific for tumor antigens is a major goal of active cancer immunotherapy. Physiologically, T cells receive promitotic and activating signals from endogenous professional antigen-presenting cells (APC) rather than directly from malignant cells. This phenomenon fits with the broader concept of cross-presentation that earlier was demonstrated for minor histocompatibility and viral antigens. Many mechanisms have been found to be capable of transferring antigenic material from malignant cells to APC so that it can be processed and subsequently presented by MHC class I molecules expressed on APC. Dendritic cells (DC) are believed to be the most relevant APC mediating cross-presentation because they can take up antigens from apoptotic, necrotic, and even intact tumor cells. There exist specific molecular mechanisms that ensure this transfer of antigenic material: 1) opsonization of apoptotic bodies; 2) receptors for released heat shock proteins carrying peptides processed intracellularly; 3) Fc receptors that uptake immunocomplexes and immunoglobulins; and 4) pinocytosis. DC have the peculiar capability of reentering the exogenously captured material into the MHC class I pathway. Exploitation of these pieces of knowledge is achieved by providing DC with complex mixtures of tumor antigens ex vivo and by agents and procedures that promote infiltration of malignant tissue by DC. The final outcome of DC cross-presentation could be T-cell activation (cross-priming) but also, and importantly, T-cell tolerance contingent upon the activation/maturation status of DC. Artificial enhancement of tumor antigen cross-presentation and control of the immune-promoting status of the antigen-presenting DC will have important therapeutic implications in the near future.

Immunosuppressive effects of interleukin-12 coexpression in melanoma antigen gene-modified dendritic cell vaccines

Genetic immunotherapy with tumor antigen gene-modified dendritic cells (DC) generates robust immunity, although antitumor protection is not complete in all models. Previous experience in a model in which C57BL/6 mice immunized with DC transduced with adenoviral vectors expressing MART-1 demonstrated a 20-40% complete protection to a tumor challenge with B16 melanoma cells. Tumors that did develop in immunized mice had slower growth kinetics compared to tumors implanted in naïve mice. In the present study, we wished to determine if the supraphysiological production of the Th1-skewing cytokine interleukin-12 (IL-12) could enhance immune activation and antitumor protection in this model. In a series of experiments immunizing mice with DC cotransduced with MART-1 and IL-12, antitumor protection and antigen-specific splenocyte cytotoxicity and interferon gamma production inversely correlated with the amount of IL-12 produced by DC. This adverse effect of IL-12 could not be explained by a direct cytotoxic effect of natural killer cells directed towards DC, nor the production of nitric oxide leading to down-regulation of the immune response - the two mechanisms previously recognized to explain immune-suppressive effects of IL-12-based vaccine therapy. In conclusion, in this animal model, IL-12 production by gene-modified DC leads to a cytokine-induced dose-dependent inhibition of antigen-specific antitumor protection.

Applications of gene transfer to cellular immunotherapy

Adoptive cellular therapy remains a potentially powerful method of eradicating established tumors. T-cells have been particularly potent effector cells, as demonstrated in animal models and clinical studies, and it is apparent that the stimulation of certain subpopulations of T-cells that are reactive to tumor antigens can lead to more therapeutic T-cells. The use of gene transfer techniques has resulted in more effective and specific methods to generate these tumor-specific T-cells. Another area of tremendous interest is in the adoptive transfer of DCs manipulated to present tumor antigen to resting, naive T-cells. Gene transfer techniques may offer more optimal ways to generate therapeutic DCs. Adoptive immunotherapy may ultimately [figure: see text] have its greatest use in patients undergoing cellular rescue after ablative chemotherapy; the infusion of immunocompetent T-cells, genetically modified stem cells, or programmed DCs may offer the opportunity to direct a patient's immune response to eliminate residual microscopic disease.

Gene therapy of hepatocellular carcinoma and gastrointestinal tumors

Primary liver cancer and liver metastases from gastrointestinal tumors lack effective therapy. Gene therapy is a promising therapeutic approach and is based on the introduction of genetic material into cells to generate a curative biological effect. Adenoviral vectors can very efficiently transduce a wide variety of malignant epithelial cells both in vitro and in vivo. A variety of gene therapy-based anticancer strategies have been effective in animal tumor models, including replacement of tumor suppressor genes, selective activation of prodrugs, genetic immunotherapy, and antiangiogenic actions. Enzymes used for genetic activation include viral thymidine kinase (tk), which may activate nucleoside analogs such as ganciclovir. We and others have demonstrated the efficacy of the tk/ganciclovir system in the treatment of hepatocellular carcinoma and metastatic colorectal cancer in experimental models. Also, this strategy can be safely applied to patients with liver tumors. Interleukin-12 (IL-12) is among the most potent cytokines in stimulating antitumor immunity. In models of primary and metastatic liver cancer we showed that intratumoral administration of recombinant adenovirus encoding IL-12 activates natural killer cells, induces specific antitumor immunity, and displays a powerful antiangiogenic effect, resulting in tumor regression. There is a synergistic effect with the gene transfer of the chemokine IP-10. Also, intratumoral injection of either dendritic cells transfected ex vivo with recombinant adenovirus encoding IL-12 (Ad.IL-12) or an adenovirus coding for the CD40 ligand have shown an intense antitumor effect against experimental colorectal cancer. In summary, a variety of gene therapy strategies have been effective against animal models of gastrointestinal tumors. Clinical trials should determine whether human patients can be treated safely and effectively by such strategies.

Gene therapy of hepatocellular carcinoma

The extraordinary versatility of gene therapy opens new possibilities for the treatment of incurable diseases, including hepatocellular carcinoma. Gene therapy strategies against tumors include prodrug activation therapy by the transfer of suicide genes, immunogene therapy, tumoral cell phenotype correction by the inhibition of oncogenes or the transfer of tumor suppressor genes, antiangiogenesis and transfer of oncolytic viruses. The experience accumulated during the last decade of clinical gene therapy indicates that genes can be expressed inside the tumor tissue, but the overall results of the studies conducted so far are still disappointing, mainly due to the poor performance of the currently available gene therapy vectors. This review covers the general aspects of gene therapy vectors, preclinical data available in animal models of hepatocellular carcinoma, and finally a brief summary of the gene therapy clinical trials aimed at the treatment of liver cancer.

Molecular therapies for colorectal cancer metastatic to the liver

Colorectal cancers are the fourth most commonly diagnosed cancers and will account for over 56,000 deaths in the United States in 2002. A majority of patients with advanced colorectal cancer develop liver metastases during the course of their disease. Treatment of colorectal cancer metastatic to the liver by surgery or chemotherapy is limited and most patients succumb to their disease. Therefore, a broad spectrum of novel treatments, including innovative molecular therapies such as gene and immunotherapy or replication-competent viral therapy, is under preclinical investigation and several clinical trials are in progress. Here we review molecular therapies for colorectal cancer metastatic to the liver.

Improved treatment of pancreatic cancer by IL-12 and B7.1 costimulation: antitumor efficacy and immunoregulation in a nonimmunogenic tumor model

Ductal pancreatic adenocarcinoma is one of the commonest and most lethal cancers in the Western world. Unfortunately, recent advances in diagnostics, staging, and therapy in pancreatic carcinoma have not resulted in significant improvements in long-term survival. We have previously shown that adenovirus (Ad)-mediated coexpression of interleukin-12 (IL-12) and the costimulatory molecule B7.1 is extremely efficient in inducing regression of highly immunogenic transplanted and nontransplanted tumors. Here, we examined the antitumor efficacy of IL-12- and B7.1-based immunotherapy against a nonimmunogenic murine model of ductal pancreatic cancer. Compared with AdIL-12 treatment alone, single intratumoral injection of AdIL-12/B7.1 led to a prolonged immune response and mediated complete regression in 80% of treated animals. After rechallenge with parental tumor cells, 70% of cured mice remained tumor-free, suggesting that protective immunity had been induced. The antitumoral response was associated with upregulation of H-2K(b) and Abcb2 expression, whereas other components of the proteasome (Abcb3, Psmb9, and Psmb8) were not affected. These data indicate that upregulation of the antigen presentation machinery by AdIL-12/B7.1 may be a therapeutic rationale for nonimmunogenic, therapy-resistant pancreatic cancer.

Gene therapy for malignant liver disease

For most patients with advanced or multifocal hepatocellular carcinoma (HCC) or with metastatic malignant liver disease treatment options are limited, resulting in a poor prognosis. Novel therapeutic strategies such as gene therapy are therefore urgently required. Gene therapeutic approaches use gene delivery systems (vectors) to introduce DNA constructs as therapeutic agents into living cells. Antitumour strategies include the reintroduction of tumour suppressor genes into tumour cells, the expression of foreign enzymes to render tumours susceptible to treatment with chemotherapeutic agents and the enhancement of tumour immunogenicity by expressing immunomodulatory genes or by genetic vaccination with tumour antigens. Furthermore, gene therapy may be also used for anti-angiogenesis to reduce tumour growth and metastatic potential. Other novel approaches aim at the development of genetically altered replication competent viruses, which selectively replicate in tumour cells inducing cell lysis. Although most clinical trials of antitumour gene therapy so far have failed to induce strong therapeutic effects, further improvement of antitumour gene therapy may finally result in potent clinical treatment options for patients with malignant liver tumours.

In vivo electroporation-mediated transfer of interleukin-12 and interleukin-18 genes induces significant antitumor effects against melanoma in mice

Direct intratumoral transfection of cytokine genes was performed by means of the in vivo electroporation as a novel therapeutic strategy for cancer. Plasmid vectors carrying the firefly luciferase, interleukin (IL)-12 and IL-18 genes were injected into established subcutaneous B16-derived melanomas followed by electric pulsation. When plasmid vectors with Epstein--Barr virus (EBV) nuclear antigen 1 (EBNA1) gene were employed, the expression levels of the transgenes were significantly higher in comparison with those obtained with conventional plasmid vectors. In consequence of the transfection with IL-12 and IL-18 genes, serum concentrations of the cytokines were significantly elevated, while interferon (IFN)-gamma also increased in the sera of the animals. The IL-12 gene transfection resulted in significant suppression of tumor growth, while the therapeutic effect was further improved by co-transfection with IL-12 and IL-18 genes. Repetitive co-transfection with IL-12 and IL-18 genes resulted in significant prolongation of survival of the animals. Natural killer (NK) and cytotoxic T lymphocyte (CTL) activities were markedly enhanced in the mice transfected with the cytokine genes. The present data suggest that the cytokine gene transfer can be successfully achieved by in vivo electroporation, leading to both specific and nonspecific antitumoral immune responses and significant therapeutic outcome.

Alpha(v)beta(3) integrin-mediated adenoviral transfer of interleukin-12 at the periphery of hepatic colon cancer metastases induces VCAM-1 expression and T-cell recruitment

We previously reported that systemic injection of recombinant adenovirus resulted in a rim of gene transduction around experimental liver tumor nodules. This zone of higher infection is dependent on the alpha(v)beta(3) integrin, acting as an adenovirus internalization receptor, which is overexpressed in tissues surrounding liver metastases. When a recombinant adenovirus encoding interleukin-12 (AdCMVIL-12) is given into a subcutaneous tumor nodule in mice also bearing concomitant liver tumors, a fraction of AdCMVIL-12 reaches the systemic circulation and infects liver tissue, especially at the malignant/healthy tissue interface. As a result of the expression at this location of the interleukin-12 transgenes, VCAM-1 is induced on vessel cells and mediates the recruitment of adoptively transferred anti-tumor cytolytic T-lymphocytes. These studies provide mechanistic explanations for the potent therapeutic synergy observed between interleukin-12 gene transfer and adoptive T-cell therapy.

Intratumoral delivery of interleukin 12 expression plasmids with in vivo electroporation is effective for colon and renal cancer

We report on an antitumor treatment involving electrogene therapy (EGT), a newly developed in vivo gene transfer method using electroporation. We carried out in vivo EGT in a subcutaneous model of CT26 colon carcinoma cells, using plasmid DNAs encoding interleukin 12 (IL-12) subunits. For this purpose, we developed two IL-12 expression systems: a cotransfer system using a plasmid encoding the IL-12 p40 subunit and a plasmid encoding the IL-12 p35 subunit, and a single-vector system using a plasmid expressing a p40-p35 fusion protein. Both transfer systems significantly inhibited the growth of CT26 tumor. Immunohistochemical analysis of IL-12 EGT-treated tumors revealed enhanced infiltration of CD8(+) cells into the tumor tissue, while reverse transcriptase-polymerase chain reaction confirmed the increased expression of interferon gamma within treated tumors. The same IL-12 EGT applied to the nude mouse model was not effective, suggesting the critical role of T cell infiltration in this treatment. The inhibitory effects revealed in experiments in which previously treated mice were rechallenged with a second inoculation of CT26 tumor cells suggested that IL-12 EGT may also establish partial systemic antitumor immunity. The growth of IL-12 EGT-treated Renca tumors, a renal cell carcinoma, was also significantly inhibited. These findings suggest that EGT of the IL-12 gene has the potential to be an effective anticancer gene therapy.

IL-12 gene therapy for cancer: in synergy with other immunotherapies

In preclinical models of cancer, gene therapy with interleukin 12 (IL-12) has reached unprecedented levels of success when combined with immunotherapy approaches such as gene transfer of other cytokines and/or chemokines, costimulatory molecules or adoptive cell therapy. These combinations have been found to produce synergistic rather than additive effects. Meanwhile, IL-12 gene therapy is beginning clinical testing as a single agent, but combination strategies are at hand.

Genetic heterogeneity in the toxicity to systemic adenoviral gene transfer of interleukin-12

Despite the efficacy of IL-12 in cancer experimental models, clinical trials with systemic recombinant IL-12 showed unacceptable toxicity related to endogenous IFNgamma production. We report that systemic administration of a recombinant adenovirus encoding IL-12 (AdCMVmIL-12) has a dramatically different survival outcome in a number of mouse pure strains over a wide range of doses. For instance at 2.5 x 10(9) p.f.u., systemic AdCMVmIL-12 killed all C57BL/6 mice but spared all BALB/c mice. Much higher IFNgamma concentrations in serum samples of C57BL/6 than in those from identically treated BALB/c were found. Causes for heterogeneous toxicity can be traced to differences among murine strains in the levels of gene transduction achieved in the liver, as assessed with adenovirus coding for reporter genes. In accordance, IL-12 serum concentrations are higher in susceptible mice. In addition, sera from C57BL/6 mice treated with AdCMVmIL-12 showed higher levels of IL-18, a well-known IFNgamma inducer. Interestingly, lethal toxicity in C57BL/6 mice was abolished by administration of blocking anti-IFNgamma mAbs and also by simultaneous depletion of T cells, NK cells, and macrophages. These observations together with the great dispersion of IFNgamma produced by human PBMCs upon in vitro stimulation with IL-12, or infection with recombinant adenovirus encoding IL-12, suggest that patients might also show heterogeneous degrees of toxicity in response to IL-12 gene transfer.

Exploiting changes in the tumour microenvironment with sequential cytokine and matrix metalloprotease inhibitor treatment in a murine breast cancer model

The study of treatment-induced changes in the tumour microenvironment might lead to effective combinations of biological therapy. IL-12 induced tumour regression and cure of an experimental murine breast cancer, HTH-K, but only after long-term treatment that was associated with chronic toxicity. During IL-12 therapy, tumour levels of the matrix metalloprotease MMP-9 declined and its inhibitor TIMP-1 was strongly induced. We therefore administered alternate cycles of IL-12 and the MMP inhibitor Batimastat (BB94) to mice. Therapeutic efficacy was increased compared with short-term IL-12 therapy but without the chronic toxicity associated with long-term IL-12 treatment. Image analysis of treated tumours revealed that BB94 prevented regeneration of tumour and stromal compartments that normally occurred after short-term IL-12 therapy.

Intratumoral coinjection of two adenoviruses, one encoding the chemokine IFN-gamma-inducible protein-10 and another encoding IL-12, results in marked antitumoral synergy

We have constructed a recombinant defective adenovirus that expresses functional murine IFN-gamma-inducible protein-10 (IP-10) chemokine (AdCMVIP-10). Injection of AdCMVIP-10 into s.c. tumor nodules derived from the CT26 murine colorectal adenocarcinoma cell line displayed some antitumor activity but it was not curative in most cases. Previous studies have shown that injection of similar s. c. CT26 tumor nodules with adenovirus-encoding IL-12 (AdCMVIL-12) induces tumor regression in nearly 70% of cases in association with generation of antitumor CTL activity. AdCMVIP-10 synergizes with the antitumor effect of suboptimal doses of AdCMVIL-12, reaching 100% of tumor eradication not only against injected, but also against distant noninjected tumor nodules. Colocalization of both adenoviruses at the same tumor nodule was required for the local and distant therapeutic effects. Importantly, intratumoral gene transfer with IL-12 and IP-10 generated a powerful tumor-specific CTL response in a synergistic fashion, while both CD4 and CD8 T cells appeared in the infiltrate of regressing tumors. Moreover, the antitumor activity of IP-10 plus IL-12 combined gene therapy was greatly diminished by simultaneous in vivo depletion of CD4+ and CD8+ T cells but was largely unaffected by single depletion of each T cell subset. An important role for NK cells was also suggested by asialo GM1 depletion experiments. From a clinical point of view, the effects of IP-10 permit one to lower the required gene transfer level of IL-12, thus preventing dose-dependent IL-12-mediated toxicity while improving the therapeutic efficacy of the elicited antitumor response.